如何在 Rust 中将函数项变成函数指针

因此，目标类型为:

pub type SkittleModuleCommand = fn(ctx: Context, msg: Message, args: Vec<String>) -> dyn Future<Output = Result<()>>

但是rust编译器指出，im试图作为参数传递的函数的类型不正确. 错误:

error[E0308]: mismatched types
  --> src/lib.rs:17:37
   |
17 |     module.register_command("ping", ping);
   |            ----------------         ^^^^ expected fn pointer, found fn item
   |            |
   |            arguments to this method are incorrect
   |
   = note: expected fn pointer `fn(serenity::prelude::Context, serenity::model::channel::Message, Vec<_>) -> (dyn std::future::Future<Output = Result<(), anyhow::Error>> + 'static)`
                 found fn item `fn(serenity::prelude::Context, serenity::model::channel::Message, Vec<_>) -> impl std::future::Future<Output = Result<(), anyhow::Error>> {commands::ping::exec}`
   = note: when the arguments and return types match, functions can be coerced to function pointers
note: method defined here
  --> /home/mcorange/@Projects/rust/autistic-bot/src/lib.rs:62:12
   |
62 |     pub fn register_command(&mut self, name: &str, comm: SkittleModuleCommand) {
   |            ^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0308`.
warning: `skittle-bot-core-module` (lib) generated 4 warnings

整个项目都在github美元.

此外，以下是可重现的最小示例:

use std::{future::Future, collections::HashMap};


pub type SkittleModuleCommand = fn(a: usize) -> dyn Future<Output = ()>;

pub async fn module_fn(a: usize) {}

fn main() {
    let mut mod_hm: HashMap<String, SkittleModuleCommand> = HashMap::new();

    mod_hm.insert(String::from(""), module_fn);

}

我试着使用变形，但我不能得到错误的类型正确.

谢谢你的帮助！